The Buttfumble is behind him, in the rearview mirror, but a world of uncertainty greeted Mark Sanchez when he walked back into the Atlantic Health Jets Training Center yesterday as the tarnished Golden Boy, his Jets career hanging by a thread, viewed more now by a team that once heralded him as its franchise quarterback as an $8.25 million albatross it cannot hope to ship to Tampa in the looming Darrelle Revis trade.

It was a good day for Revis, getting a green light to begin running on his surgically-repaired left knee — ostensibly to the Tampa Bay Independence Bank — and a good day for Sanchez in that he didn’t find the locks changed on him when he showed up.

Because it isn’t his team anymore, and it isn’t his job anymore for the first time since he arrived in 2009. His buddy Dustin Keller is a Dolphin, Rex Ryan is a lame duck, Santonio Holmes is nowhere in sight, Marty Mornhinweg will be his third offensive coordinator in three years, Revis is on his way out the door, an unforgiving fan base in a town without pity will be waiting in ambush … and yet Sanchez wouldn’t want a fresh start, an escape from New York, as much as Tim Tebow does.

Not to mention the possibility that if and when general manager John Idzik pulls the trigger on the Revis deal between now and next Thursday’s NFL draft, the Jets, armed with two first-round picks, might be tempted to select Geno Smith, E.J. Manuel or Ryan Nassib to join David Garrard, Greg McElroy and Matt Simms in the full-fledged summer quarterback duel.

And yet, here comes Sanchez, battered and bleeding the last time we saw him, spoiling for the fight of his life, announcing “BRING IT ON!” loud enough to hear without a green-and-white megaphone.

“My heart and soul is into this thing,” Sanchez said. “I’m fired up about this year and hope it’s a good one.”

Back to the future, when he was the talk of this town.

“It’s a great place to play when you’re winning,” Sanchez said. “It’s also tough when you’re not playing as well as you like to and things aren’t going your way.”

Because things didn’t go his way the past two seasons (52 turnovers), Sanchez almost immediately found himself having to answer a question about the rumors of his name being tossed around as part of the Revis deal which, if true, would not have been tossed around first by the Bucs.

“I don’t know what to say,” Sanchez said. “That’s more of an upstairs question. I’m not really worried about that.”

The follow up: Did you ask for a clarification?

“No,” Sanchez said.

He’s a good guy, and more power to him if he can get off the deck and heal any remaining emotional scars and write a story of resurrection and redemption against all odds. He was babied and coddled for four years. The honeymoon is over for him, and he knows it. So, he worked with Jeff Garcia to help him learn the West Coast system.

“I’m coming in to compete and be the best player I can,” Sanchez said. “It’s my job to be the most accurate guy, the best decision-maker. Then we’ll see what happens.

“You approach this thing like it’s yours, and that’s how you got to feel.”

Idzik’s mantra is Competition Through and Through.

“I think it’ll bring out the best in everyone on the team,” Sanchez said. “I totally respect that. I’m just preparing to play well for this team.”

The evidence on tape was damning when Sanchez watched the nightmare replays after the season.

“There’s nothing else to do except try and improve and try to understand how you got in that position and what led to that and how to avoid some of those pitfalls if possible,” he said.

It starts with throwing the ball only to your own teammates and holding on to it.

“We didn’t quite develop an identity,” Sanchez said. “At times there were decisions I made that put our team in a tough position.”

At least he won’t have to worry about Revis intercepting him in the New York Super Bowl.

“I love him as a teammate, I love him as a friend. … I don’t make those decisions,” Sanchez said.

There were no more questions for him.

“You guys went light on me,” Sanchez said. To which The Post’s Brian Costello chimed in: “Give us time.”